I run full 3 inch mandrel bent with a 3 inch X-pipe. I turn immediately toward passenger side with both pipes, then run down the frame rail side by side, then back to normal position behind the tranny. There is plenty of room for 3 inch.
Originally I did this with a Dynomax kit did this in the 80s with 2.25 and no crossover, I copied the concept when I did big pipes. I used to cross the left and right side, left bank/right outlet. I used to think it was better to keep them sort of equal length, but couldn't do that with the 3 inch and I think the X-pipe does me good anyway. This is a shortbed 4x4 with a married case, I would expect an F250 to have more room
These of course are laying upside down on the floor and miserable Flowmasters live on the shelf awaiting anyone else but me